Method for locating and supporting tendons in reinforced concrete structures

ABSTRACT

A method is provided for locating and supporting tendon members in joist-forming channels of a concrete form. At spaced intervals tendon sections are received on suspension-type tendon supports. Means are provided for lifting the tendon sections into predetermined positions of vertical adjustment relative to the bottom of the joist sections. In this position, the lifted tendon sections are securely held against lateral displacement while concrete is being poured into the form. The suspension-type tendon support apparatus comprises upper rigid suspension bar elements transversely engageable across upper sides of the concrete form to bridge the joist-forming channels in the form, and provide a footing for workmen. The tendon supporting elements depending from the suspension bar elements may be drawn upwardly either by hand or by a power tool into any desired position of vertical adjustment to facilitate rapid and accurate positioning of tendon sections, and a workman&#39;&#39;s labor is greatly simplified.

United States Patent Laderoute METHOD FOR LOCATING AND SUPPORTINGTENDONS lN REINFORCED CONCRETE STRUCTURES Maurice Laderoute, I I8Samosct Ave., Hull, Mass. 02045 Filed: Apr. 20, 1973 Appl. No.: 352,926

Related U.S. Application Data Continuation-impart of Ser. No, 295,441,Oct. 6, 1972.

lnventor:

U.S. Cl. 29/155 R, 249/91 References Cited UNITED STATES PATENTS PrimaryExaminer-Thomas H. Eager Attorney, Agent, or Firm-Munroe H. HamiltonABSTRACT A method is provided for locating and supporting tendon membersin joist-forming channels of a concrete form. At spaced intervals tendonsections are received on suspension-type tendon supports. Means areprovided for lifting the tendon sections into predetermined positions ofvertical adjustment relative to the bottom of the joist sections. Inthis position, the lifted tendon sections are securely held againstlateral displacement while concrete is being poured into the form. Thesuspension-type tendon support apparatus comprises upper rigidsuspension bar elements transversely engageable across upper sides ofthe concrete form to bridge the joist-forming channels in the form, andprovide a footing for workmen. The tendon supporting elements dependingfrom the suspension bar elements may be drawn upwardly either by hand orby a power tool into any desired position of vertical adjustment tofacilitate rapid and accurate positioning of tendon sections, and aworkmans labor is greatly simplified.

5 Claims, 22 Drawing Figures PATENTED JANZ 8 I975 sum '3 or 5 I!!!Ill/fl METHOD FOR LOCATlNG AND SUPPORTING TENDONS IN REINFORCED CONCRETESTRUCTURES This invention is a continuation-in-part of my copendingapplication Ser. No. 295,441 filed Oct. 6, 1972, entitled METHOD ANDAPPARATUS FOR SUPPORTING TENDONS IN REINFORCED CON- CRETE.

The instant invention relates to methods and apparatus for use informing reinforced concrete structures. More particularly, the inventionis concerned with methods and means for supporting and positioningreinforcing tendons and reinforcing rods of the class commonly employedin reinforcing concrete structures such as is exemplified by a joist andslab type of concrete construction.

As is well-known to those skilled in the art, it is customary topost-tension concrete masses which have been poured into a concrete formof some desired shape, and this is accomplished, in the joist and slabtype of construction, for example, by locating steel tendon members inthe joist forming portions of the form. Concrete is then poured andallowed to set until a suitable strength is realized. Thereafter, thetendon members are tensioned by hydraulic ram means or other suitabledevices.

A highly important consideration in using a steel tendon is the matterof supporting the tendon in the joist forming section of the concreteform in a raised position relative to the bottom surface of the joistforming channel. This is customarily done by locating spaced apartsections of the tendons at varying positions of vertical adjustment inaccordance with force stressing tables provided with engineeringdrawings of the structure being built.

Presently in use are tendon-supporting devices which are referred to inthe trade as chairs and which are furnished in varying sizes. Each chairis made of wire-like sections formed into a U-shape and arranged atright angles to one another to provide four supporting legs whose lengthcan be varied as desired to provide varying heights. At their point ofcrossing the wire sections are formed with a tenton-supporting cradlefor receiving and supporting a section ofa tendon thereon.

Problems arise in connection with locating the chairs in the joistsections since the various stressing tables may include a wide range ofvertical spacings, and therefore, the chairs have to be made availablein all of these sizes. The operation of selecting chairs of correct sizeand locating these chairs of different heights in the bottom of theconcrete form is time consuming and requires that the workman be on hisknees under difficult working conditions. It is also necessary to secureeach chair cradle to its supported tendon section by wire or othermeans, and since this may be necessary at spacing of every 6 feet, forexample, a very considerable amount of time is used up in positioningtendons with the chair-support method. There is also the frequentoccurrence of chairs being displaced or tipped over when concrete ispoured, and this can lead to faulty post-tensioning and other problems.

It is a chief object of the invention to provide improved methods forsupporting tendons in a concrete form in place of chairs commonlyemployed for this purpose.

LII

Another object of the invention is to devise a method of handlingtendon-supporting structures which may be employed in a single size andwhich can be drawn into vertically adjusted positions to provide a widerange of supporting heights required for a post-tensioning operation.

Still another object is to provide a method which can be utilized by aworkman from a point immediately above a concrete form with less laborand time being required to make necessary locations.

And still another object of the invention is to provide a method ofhandling a tendon-supporting apparatus having an adjustabletendon-lifting element which can be drawn upwardly by hand ormechanically raised to a desired point by a rotary driving force exertedthrough a power tool of conventional nature.

It is still another object of the invention to devise a method ofhandling a tendon-supporting and lifting apparatus which may alsoinclude means for retaining a plurality of tendons in side-by-siderelationship and also for simultaneously receiving and retaining one ormore retaining rods located at points below the tendon members.

With the foregoing objectives in mind, I have conceived of improvedmethods and means for supporting and locating tendon sections in areinforced concrete structure such as, for example, a joist and slabtype wherein a concrete form presenting joist-forming channels separatedby flat bridging sections is secured to a horizontal shoring structure.

ln accordance with the invention, tendons are placed in thejoist-forming channels in the usual manner. However, instead ofpositioning the conventional type chairs in the joist channel andlifting tendon sections up onto the chairs and thereafter tieing thetendons to respective chair cradles, the chairs are completelyeliminated.

Tendon sections are engaged at their under sides by means of tendonholder elements. Each holder element and engaged tendon section issupported from a suspension bar opposite ends of which are solidlyreceived on upper sides of adjacent bridgeing sections of the concreteform. With this arrangement of parts, a tendon section may be located ina desired position of vertical adjustment in several ways. ln somecases, the tendon holder may be secured to the suspension bar in fixedrelationship.

The length of the tendon holder portion depending from the suspensionbar thus determines the position of vertical adjustment of the tendonand the depending lengths may occur in a range of sizes. In otherinstances, a preferred procedure is to position a tendon section on theholder and then raise or lift both the holder and the supporting sectionup to a desired point or spacing from the bottom of the channel. Thismay be accomplished either manually or by exerting mechanical forces.When all of the sections of a tendon to be raised have been positionedby one of the other of these methods, it will be understood thatconcrete is poured covering the holders and suspension bars. After theconcrete has set to a desired strength the tendons are post-tensioned inthe customary manner.

As noted above, the invention includes means for adjustingtendonplacement both manually and by mechanical forces and in onedesirable form of the invention, the use of mechanical forces is carriedout.

An important feature of my improved method of positioning and supportingtendon sections at desired points is the use of a rotary driving forceexerted from points above the concrete form to raise the holder elementsand tendon sections as required in one simplified manual operation.

In this connection, I have devised a tool for engaging atendon-supporting component and applying a rotary driving force by meansof a power tool of well-known construction.

The nature of the invention and its other objects and novel featureswill be more fully understood and appreciated from the followingdescription of a preferred embodiment of the invention selected forpurposes of illustration and shown in the accompanying drawings, inwhich:

FIG. 1 is a fragmentary perspective view illustrating a first step informing a reinforced concrete structure of the joist and slab type inwhich reinforcing rods and reinforcing tendons have been laid in channelportions of a concrete form indicated fragmentarily and being secured toshoring members;

FIG. 2 is a detail perspective view of tendonsupporting apparatus of theinvention for use in the concrete form structure of FIG. 1;

FIG. 3 is a side elevational view of the concrete form and shoringindicated fragmentarily and illustrating the steps of locating thetendon-supporting apparatus of FIG. 2 in the concrete form in engagementwith tendon members;

FIG. 4 is a detail cross section taken on the line 4-4 of FIG. 3;

FIG. 5 is a fragmentary plan view of one of the tendon-supporting unitsinstalled;

FIG. 6 is another elevational view of the concrete form and illustratingsteps of lifting successive tendon sections into varying positions ofvertical adjustment relative to the respective channel bottom of theform by means of a rotary driving force;

FIG. 7 illustrates the steps of pouring concrete while the tendons areheld in positions in vertical adjustment;

FIGS. 8 and 9 are detail views of modification of tendon-supportingstructures;

FIG. 10 is a cross section taken on the line 10-10 of FIG. 6;

FIGS. 11 14, inclusive, illustrate still another modification for use insupporting both reinforcing tendons and reinforcing rods;

FIGS. 15 is a detail view illustrating the tendon supporting apparatusof the invention utilized as a means for supporting additionalcross-laid rod members at the upper side thereof;

FIG. 16 is a fragmentary detail view of a modified form of suspensionbar means;

FIG. 17 is a perspective view of a modified means for supporting atendon means;

FIG. 18 is a lifting frame for manually raising the supporting means ofFIG. 17;

FIGS. 19 to 22 illustrate still other modified forms of the invention.

The combination of parts shown in FIGS. 1 to 16 constitute one desirableform of apparatus for carrying out the method of the invention, andFIGS. 17 to 22 illustrate other desirable forms of the invention. Theprincipal parts of this embodiment of tendonsupporting apparatus shownin FIGS. 1 to 16 include suspension bar means for engagement at theupper side of a concrete form of the joist and slab type, and tendonholder means received in the suspension bar means in a dependingposition, and means for locating the tendon holder in a desired positionof vertical adjustment relative to the suspension bar means.

Considering the structure of FIGS. 1 to 16 in more detail, referencecharacter F generally indicates a concrete form of the joist and slabtype supported on shoring means 2, as is most clearly shown in FIG. 1.As will be observed from an inspection of this FIGURE. the form F ismade with joist-forming channel sections as 4, 6, 8, etc., and thesechannel sections are connected together by upper flat bridging sectionsas l0. l2 and 14. The channel sections are formed with retaining edgesas l6, 18 (FIG. 10) anchored in shoring strips as 22, 24, transverselysecured over the shoring timbers 2. Numerals 30, 32 and 34 denote steelreinforcing rods of the type commonly employed in reinforced concreteconstruction to impart desirable tensile strength. Numerals 36, 38 and40 refer to steel tendons consisting of steel strands which are utilizedfor post-tensioning concrete in the joist-forming portions after theconcrete has been poured and allowed to set to a predetermined strength.

In FIG. 2, I have shown one of the tendon-supporting units of theinvention removed from a concrete form and FIGURES 3 to 7 show a numberof tendon-holding units combined with the concrete form F in operativepositions. As may be most clearly seen from an inspection of FIG. 2,there is provided a suspension bar member denoted by the numeral 42, andthis bar is made of a size such that it may rest upon two adjacentbridging sections of the form in the manner indicated in FIG. 3.

The suspension bar member 42, in one preferred form, may be of achannelled cross section. as shown. and is designed to have sufficientstrength to receive the weight of workmen without bending or breaking.It is intended that other cross-sectional shapes may also be used.

Loosely disposed in the suspension bar 42 is a tendon holder 44 formedwith a hooked lower extremity 46 for underlying and supporting a sectionof a tendon member. It will be observed that the suspension bar 42 isformed with air-vent apertures as 42a and 42b and also with a centrallydisposed opening through which an upper end of the tendon holder 44 isreceived and is free to move. The tendon holder, throughout a portion ofits length, may be threaded, and threadably engaged about the projectingupper end 44a of the holder is a washer and nut assembly 48 which restsupon an upper side of the suspension member 42. Extending downwardlyfrom the lower end of the suspension bar are channel engaging stops as50 and 52. Also secured at the bottom of the hooked portion 44 is atransverse stop part 54 which is designed to fit into opposite sides ofa channel bottom and secure the hooked end 46 in a centered position.

FIG. 3 illustrates the tendon support of FIG. 2 installed in channelportion 6 with the stop elements 50 and 52 engaged against oppositeinner sides of channel 6 and with the suspension bar 42 located acrossthe bridging portions l0 and [2. Transverse stop 54 is also shown inengagement with the bottom of the channel. This Figure is also intendedto illustrate the step of locating a section of tendon 38 on the hookedportion 46 of holder 44. A second unit having the same but primednumerals is shown at the right hand side of FIG. 3. In

FIG. 4 the raised section of holder 38 is shown in one position ofpredetermined vertical adjustment.

It will be understood that sections of the tendon 38 may be required tobe vertically positioned at intervals of, of example, every 6 feet, andin each such case, a different height may be specified. There is thuscreated a need for using a plurality of tendon supports each of whichhas to be positioned at different vertical heights.

In FIG. 6, there is illustrated in more detail steps of positioning aseries of tendon supports by the invention method. As noted therein,suspension bars 42, 42' and 42" are placed on bridging sections as 10,I2 and 14 and engaged with sections of tendons 36, 38, 40, each of whichis shown positioned at different levels.

In accordance with the invention, I provide for lifting the hookedholder portion by means of a rotary drive force exerted through aspecial driver frame which is designed to be powered by a drill or otherrotary power tool. As shown in FIG. 6, the driver frame is denoted bynumeral 70 and includes spaced vertical supporting legs having a nutengaging part for engaging over and gripping the nut 48". At its upperend, the frame 70 is provided with a stud portion 76 which is designedto be held in the chuck of a drill 78.

When the drill or other power tool is operated, it will be apparent thatthe frame turns about a vertical axis and threads the part and nut 48"around the correspondingly threaded portions of the holder 44", thuscausing this member to be drawn upwardly through the suspension bar. Thetendon section 36' is thereby lifted to some desired height.

As illustrated at the right hand side of FIG. 6, I may also provide inthe frame 70 a scale of varying heights as suggested at 80, and slidablysupported over this scale portion of the frame, I may further provide anindicator bar 82 which can be raised to a predetermined height andsecured by a wing nut or other fastening 82a. By means of thisarrangement, it will be apparent that a workman may very rapidly liftgiven tendon sections to predetermined heights by simply engaging theframe and rotating it with a power tool until the upper end of theholder 44" comes into contact with the member 82. It is pointed out thatthis whole operation, including the step of placing the suspension bar,engaging a tendon in the holder, and raising these two parts, is carriedout in a comfortable and convenient working position for an operator,and this results in more rapid installation and substantial savings inlabor costs.

After all of the tendons in a given construction area have been liftedinto desired positions, the projecting upper ends of the holder elementsmay be bent over as suggested by the holder element 44 in FIG. 6 andconcrete is then poured to completely cover the tendons and suspensionbars and holders as suggested in FIG. 7. In this FIGURE, concrete joistportions are denoted by the numerals 3, 5, 7, and an overlying slabportion is denoted by the numeral 9.

It will be understood that concrete thus poured is allowed to set in theusual manner until is acquires a suitable tensile strength and then thetendons as 36, 38'and 40 are stressed by means of hydraulic ram means.

It is also intended that the invention structure may be modified invarious ways. For example, I may provide a holder element 73 with alooped stop part 75, as illustrated in FIG. 8. The part 75 engagesagainst opposite sides of a channel 75a in the manner earlier describedwith reference to the transverse stop 54.

l may also provide for lifting a tendon section as shown in FIG. 9wherein a hooked portion 77 is secured to a threaded sleeve member 79having a transverse stop part 770 Since the hooked portion 77. whensupporting a tendon section 81, cannot turn until the threaded sectionof the holder 83 is rotated, sleeve portion 79 and tendon section 77 canbe lifted into a desired position of vertical adjustment.

In FIG. 11, I have illustrated an arrangement including a holder element85 and tendon 86. The threaded sleeve 87 suspended as earlier describedfrom a suspension bar 89 provides for vertical adjustment. The sleeve 87is also constructed with an aperture for loosely receiving and guiding asecond holder element 91 which may also be used to engage and hold abottom reinforcing rod as 93. Where is is desired to lift both areinforcing rod and tendon, I may provide a holder 95, as shown in FIG.12, with a hooked end 97 for supporting atendon 99, and secured to themember 95 by welding or other suitable means is a second hooked portion101 for reinforcing rod- 103. Both the rod and the tendon may be raisedsimultaneously where this is desired.

InFlG. 13, there is illustrated a holder member 88 having a threadedsleeve as 90 and a suspension bar 97. A hooked portion 94 supports atendon 96a. Also mounted loosely around the holder 88 at the lower endthereof is provided a sleeve having a hooked end 98 for supporting areinforcing rod 102.

In FIG. 14, I have shown a suspension bar 105 in which is supported twoholder elements 107 and 109, bothv of which may be threaded and receivedthrough a sleeve 108. Both the holders 107 and 109 are provided withthreaded driver members 111 and 113, respectively, which rest upon thebar 105 as shown. With this arrangement, either one of the holderelements may be independently raised through the suspension bar and eachof these members may be provided with tendon hooks as shown.

In FIG. 15, there is illustrated a type of reinforced concreteconstruction sometimes employed in buildings in which suspension bars as115, I17 and 119 are mounted on a concrete form 120 and at their uppersides the suspension bars may receive cross-laid rods as 122, and overthese rods another set of reinforcing rods as 124, 126, etc., may beinstalled.

In FIG. 16, I have shown a modified form of suspension bar which isprovided with a stamped-out vertically depending stop portion 132 forengagement with a channelled section of a form.

As earlier suggested in the specification, it may be desired in someinstances to raise or lift tendon sections by a manually exerted forcerather than using power driven rotary forces as employed with thestructures illustrated in FIGS. 1 to 16.

To provide for lifting a tendon section by hand, I have further deviseda modified lift rod apparatus in the form illustrated in FIGS. 17through 22. In general, this lift rod apparatus includes a channelledsuspension bar of the type earlier described, tendon holder meansreceived through the suspension bar, a lift rodand handle engageablewith the holder means and a frame structure by means of which a tendonsection may be lifted to a desired position of vertical adjustment.

Referring more in detail to FIGS. 17 and 18, numeral 11 denotes asuspension bar member which may be of channelled cross section similarto the suspension bar 42 in FIG. 2. At its upper side, there is formedan elongated slot 13 through which is loosely received a lift rodelement 35 formed with a hooked upper end 17. Also provided are ventholes 110 and 11b. A split lock washer 19 is slidably engaged around therod 35 in a position to allow the rod to be pulled upwardly and toprevent downward movement of the rod through the suspension bar.

At its lower end the lift rod element is formed with curvedtendon-retaining parts 21 and 23 which are arranged to definetendon-retaining spaces 25 and 27 into which tendon sections may belocated. The tendon-retaining sections have attached along bottomportions thereof a spreader member 29 which is of a size designed toengage between the sides of a channel in which the apparatus may bedisposed. Also provided are two U-shaped spreader elements 31 and 33which are secured at the upper side of the suspension bar in a positionto fit against opposite channel sides over which the suspension bar isplaced. These spreaders 31 and 33 are arranged to maintain the bar in asubstantially right-angularly disposed position with respect to thechannel.

In combination with the tendon holder 15, 1 provide a lift rod 35 showntogether with a channel member 11 in FIG. 18. The lift rod 35 isreceived through suspension bar 11 as shown and is formed at its lowerend with a hooked part 37 for interlocking with the hooked end 17 ofthetendon holder 15. At its upper end, the lift rod 35 is provided with ahandle 39 by means of which the tendon holder 15 and the lift rod 35 maybe pulled upwardly through a frame structure. The frame structure isformed with an annular head 41 in which the lift rod 35 is slidablyguided. Extending downwardly from the head 41 are spaced apart sides 43and 45 which terminate in supporting feet 49 and 51. The side 43 isprovided with a scale and an adjustable stop 47. The stop 47 is movablealong the frame into positions of register with the scale and can besecured by a thumb nut 47a. lt will be observed that the supporting feet49 and 51 are designed to bear against the upper side of the channelsuspension bar 11 when the lift rod is raised.

By means of this arrangement, the tendon support 15 when attached to thelift rod 35 can be raised into a desired position of vertical adjustmentdetermined by the location of the adjustment stop 47 to thus position atendon section in accordance with engineering specifications.

ln some instances, it may be desired to support tendons in side-by-siderelationship and in FIG. 19 there is illustrated means for doing this.As shown in FIG. 19, a handle 39, lift rod 35 and suspension bar 11 arecombined with a modified form of tendon holder 15a in which there isprovided a triangularly-shaped holding part 53. The part 53 has a hookedend 55 which can be moved into and out of interlocking relationship, assuggested in dotted lines.

Supported in the base of part 53 are spaced apart tendon-retaining clips57, 59 and 61 in which a set of three tendons may be securely placed andheld beside one another in aligned relationship. A spreader 63 is alsoprovided with the part 53.

FIG. 20 illustrates another tendon holder 65 for holding tendons inside-by-side relationship and for rigidly bracing opposite ends of ahorizontal retaining rod 67 on which tendon clips 69, 71 and 73 aresupported. A vertical brace 75 is arranged, as shown, to provide reinforcement at the underside of rod 67.

In FIGS. 21 and 22, still another tendon supporting holder 79 forsupporting a larger number of tendons in side-by-side relationship isillustrated. The holder 79 is received through a rigid bar element 81 onwhich are located tendon clips 83, 85, 87 and 89.

1 claim:

1. In a method of forming a reinforced concrete structure of the joistand slab type wherein a concrete form presenting joist forming channelsseparated by flat bridging sections is secured to a horizontal shoringstructure and reinforcing tendons are placed in the joist formingchannels and raised into predetermined positions of vertical adjustment,the steps which include locating a tendon member in a joist formingchannel of a concrete form between two adjacent bridging sections of theconcrete form and below upper surfaces of the adjacent bridgingsections, engaging an underside of said tendon in the joist formingchannel with a tendon holder member, suspending the tendon holder andengaged tendon section in suspension bar means supported at spaced apartpoints at upper sides of two adjacent flat bridging sections of theconcrete form and then lifting the engaged tendon sections and tendonholder while suspended into a position of predetermined vertical spacingwith respect to the bottom of the joist forming channel.

2. A method according to claim 1 in which the engaged tendon section andtendon holder are lifted by rotating an internally threaded elementabout a threaded section of the tendon holder.

3. A method according to claim 1 in which the engaged tendon section andtendon holder are suspended at spaced apart points from said suspensionbar member and an internally threaded element mounted at the upper sideof the suspension bar member. and said tendon holder and engaged tendonsections being lifted by rotating the internally threaded member about athreaded section of the tendon holder.

4. A method according to claim 3 in which the internally threadedelement is rotated by engaging it in the bottom of a revolving frame anda rotary driving force is applied at the top of the frame to turn saidframe about a vertical axis of rotation.

5. A method according to claim 2 in which the engaged tendon section andtendon holder are held in a fixed position between two adjacent channelsides.

1. In a method of forming a reinforced concrete structure of the joistand slab type wherein a concrete form presenting joist forming channelsseparated by flat bridging sections is secured to a horizontal shoringstructure and reinforcing tendons are placed in the joist formingchannels and raised into predetermined positions of vertical adjustment,the steps which include locating a tendon member in a joist formingchannel of a concrete form between two adjacent bridging sections of theconcrete form and below upper surfaces of the adjacent bridgingsections, engaging an underside of said tendon in the joist formingchannel with a tendon holder member, suspending the tendon holder andengaged tendon section in suspension bar means supported at spaced apartpoints at upper sides of two adjacent flat bridging sections of theconcrete form and then lifting the engaged tendon sections and tendonholder while suspended into a position of predetermined vertical spacingwith respect to the bottom of the joist forming channel.
 2. A methodaccording to claim 1 in which the engaged tendon section and tendonholder are lifted by rotating an internally threaded element about athreaded section of the tendon holder.
 3. A method according to claim 1in which the engaged tendon section and tendon holder are suspended atspaced apart points from said suspension bar member and an internallythreaded element mounted at the upper side of the suspension bar member,and said tendon holder and engaged tendon sections being lifted byrotating the internally threaded member about a threaded section of thetendon holder.
 4. A method according to claim 3 in which the internallythreaded element is rotated by engaging it in the bottom of a revolvingframe and a rotary driving force is applied at the top of the frame toturn said frame about a vertical axis of rotation.
 5. A method accordingto claim 2 in which the engaged tendon section and tendon holder areheld in a fixed position between two adjacent channel sides.